JP2009147986A - Image processing device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image processing device for filtering image data by a single filtering means while properly switching filtering before the image data are compressed and after the image data are expanded. <P>SOLUTION: In an image reading device 1, inputted digital image data are subjected to lossy compression in a compression section 63 and stored in a storage section 64. The compressed image data in the storage section 64 are expanded in an expansion section 65 and outputted. When predetermined filtering is performed on the digital image data in a filtering section 62, the filtering is performed by properly switching pre-filtering performed before the image data are compressed and post-filtering performed after the image data are expanded. Therefore, pre-filtering and post-filtering can be properly switched by the single filtering section 62 according to characteristics of the image data to be processed, thereby improving image quality at low cost. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an image processing apparatus, and more particularly, to an image processing apparatus that performs filter processing on image data by appropriately switching before and after compression of image data by a single filter processing unit.

In an image processing apparatus such as a scanner or a copying apparatus, the read image is compressed and temporarily stored in an image memory. Thereafter, the compressed data is read out from the image memory and decompressed for use in recording output, or in a computer or the like. Outputting to an external device.
When the image is compressed / expanded in this way, it can be divided into lossless compression and lossy compression depending on whether the image is the same as the original image before or after compression / expansion.
On the other hand, in an image processing apparatus that handles digital data, filter processing such as edge enhancement processing is an important function.
For example, in an MFP system having a composite function such as a printer function for accumulating multi-valued images, a scanner function, and a facsimile function, the filter preprocessing type shown in FIG. 9 depends on the positional relationship between the filter processing and compression / decompression processing. And the two types of filter post-processing types shown in FIG.

In the filter preprocessing type, as shown in FIG. 9, the MFP system 100 performs filter processing on the image data read by the reading device 101 by the filter processing unit 102, and compresses the 8-bit data by the compressor (code). Compressor) 103 and store in external storage device 104. Thereafter, the MFP system 100 reads the accumulated data from the external storage device 104, decompresses it with the decompressor (decoder) 105, and performs gradation conversion processing (with gradation conversion processing unit 106 on the expanded 8-bit data ( Error diffusion processing) is performed, and the writing device 107 prints out.
In the post-filter processing type, as shown in FIG. 10, 8-bit data obtained by compressing image data read by the reading device 101 by the compressor 103 is stored in the external storage device 104. The MFP system 100 then reads the accumulated data from the external storage device 104, performs filter processing on the 8-bit data decompressed by the decompressor 105, and performs tone conversion by the tone conversion processing unit 106. Processing (error diffusion processing) is performed, and the writing device 107 prints out. In FIG. 9 and FIG. 10, the same components are denoted by the same reference numerals.

When the compression / decompression portion by the compressor 103 and the decompressor 105 is lossless compression, the print output results are the same for the filter preprocessing type and the filter postprocessing type. However, when the compression / decompression part performs irreversible compression, the print output result is not the same between the pre-filter processing type and the post-filter processing type, resulting in different image quality. In this way, in the case of lossy compression, the print output results differ between the filter preprocessing type and the filter postprocessing type because the lossy compression is stored in exchange for the loss of some frequency components. This is because the image data size to be processed is reduced.
As described above, in a system that performs accumulation by lossy compression, whether the filter processing is performed before or after the compression and decompression has a large influence on the characteristics of the output data is an important factor.
In general, irreversible compression often loses high-frequency components. For example, the sharpness of the edge of a character tends to decrease.
Therefore, in order to correct the reduction in the sharpness of the edge, as shown in FIG. 11, the filter processing unit 102 takes into account the loss of high-frequency components due to lossy compression in advance in the image data read by the reading apparatus 101. Thus, a strong edge enhancement filter process is applied to the original image, and then compressed by the compression unit 103 and stored in the external storage device 104. The image data in the external storage device 104 is decompressed by the decompressor 105, the printer γ conversion unit 108 performs printer γ conversion processing, and the gradation conversion processing unit 106 performs gradation conversion processing. Print out with.
In this way, when filtering is performed in the previous stage, even if edge enhancement is applied to the lost information, it is avoided that there is a limit in improving the sharpness of the character, and deterioration of the sharpness of the character is suppressed. In addition, the image quality can be improved.

Further, when performing processing (hereinafter referred to as adaptive γ conversion processing) for switching image processing (for example, a printer γ conversion table for adjusting output density) depending on whether it is edge or non-edge, filter processing is performed for cost reduction. In some cases, the FIFO is used to determine whether or not an edge is detected.
For example, as shown in FIG. 12, the image data read by the reading device 101 is directly compressed by the compression unit 103 and stored in the external storage device 104. After the image data in the external storage device 104 is decompressed by the decompressor 105 and subjected to filter processing by the filter processing unit 102, it is determined whether or not it is an edge using the FIFO of the filter processing unit 102, and the determination result is obtained. Accordingly, the adaptive γ conversion unit 109 performs adaptive γ conversion processing, the gradation conversion processing unit 106 performs gradation conversion processing, and the writing device 107 performs print output.
If the processing is performed in this way, the γ conversion table used for the character portion and the pattern portion is different, so that a density suitable for each region can be obtained, and the image quality of a mixed character / photo original is improved. be able to.
However, since the printer γ conversion process is a function for adjusting the print density, an image processing apparatus that accumulates 8-bit data, for example, the MFP system 100 shown in each of the above drawings, performs the printer γ conversion process in advance in the preceding stage. It is necessary to do it later.
In the filter post-processing type, both the filter processing and the adaptive γ conversion processing are performed in the subsequent stage.

However, in the above conventional technique, in order to improve the image quality, it is necessary to switch both the filter preprocessing type and the filter postprocessing type appropriately according to the image. In order to switch the filter post-processing type appropriately, as shown in FIG. 13, it is necessary to provide the filter processing units 102a and 102b in both the previous stage and the subsequent stage, and a FIFO is prepared for each of the filter processing units 102a and 102b. There is a need. As a result, there is a problem that the cost of the image processing apparatus is increased.
Therefore, the present invention uses one filter processing means in the former stage and the latter stage, and implements by appropriately switching between a filter preprocessing type specialized for character originals and a filter postprocessing type suitable for character photo mixed originals, An object of the present invention is to provide an image processing apparatus capable of improving image quality at low cost.
Specifically, according to the first aspect of the present invention, the input digital image data is irreversibly compressed by the compression means and stored in the image data storage means, and the compressed image data of the image data storage means is expanded. When the digital image data is subjected to predetermined filter processing by the filter processing unit, the filter processing is performed before compression by the compression unit, and the filter processing is performed after the expansion by the expansion unit. By appropriately switching between post-filter processing to be performed, one filter processing means switches between pre-filter processing and post-filter processing according to the characteristics of the image data to be processed, thereby improving image quality at low cost. Thus, an object of the present invention is to provide an image processing apparatus that can obtain an output having characteristics expected by a user at low cost.
According to the second aspect of the present invention, when the image data information is mainly character information, the image sharpness of the image data whose main information is characters is obtained by performing pre-filtering processing on the image data. An object of the present invention is to provide an image processing apparatus that can further improve image quality at low cost.
According to a third aspect of the present invention, when image data information is mainly text information and photo information, post-filter processing is performed on the image data so that the main information is text data and photo. An image processing device that improves the sharpness of characters and reduces the moire of halftone photos, improves the image quality of both characters and photos at a low cost, and further improves the image quality at a low cost The purpose is to do.

In order to solve the above-mentioned problems, an image processing apparatus according to the first aspect of the present invention is an irreversible compression of input digital image data by a compression unit and stores the digital image data in the image data storage unit. The compressed image data is decompressed by the decompression means and output, and the image processing apparatus includes a filter processing means for performing a predetermined filter process on the digital image data, wherein the filter processing by the filter processing means The above object is achieved by appropriately switching between pre-filter processing performed before compression by the compression means and post-filter processing performed after decompression by the decompression means.
According to the above configuration, the input digital image data is irreversibly compressed by the compression means and stored in the image data storage means, and the compressed image data of the image data storage means is decompressed by the decompression means and output. When the filter processing means performs predetermined filter processing on the digital image data, the filter processing is performed before the compression by the compression means, and the filter post-processing is performed after the decompression means performs the filter processing. Since switching is performed as appropriate, it is possible to switch between pre-filter processing and post-filter processing according to the characteristics of the image data to be processed with a single filter processing means, thereby improving image quality at low cost and low cost. Output of the characteristics expected by the user can be obtained.
In this case, for example, as described in claim 2, the image processing apparatus performs the pre-filtering process on the image data when the information on the image data is mainly character information. There may be.
According to the above configuration, if the image data information is mainly character information, filter preprocessing is performed on the image data, so that the sharpness of the characters of the image data whose main information is characters is improved. The image quality can be further improved at a low cost.
Further, for example, as described in claim 3, when the information of the image data is mainly character information and photo information, the image processing device performs the post-filtering process on the image data. It may be a thing.
According to the above configuration, if the image data information is mainly character information and photo information, post-filtering processing is performed on the image data, so that the main information is the character data of the image data. The sharpness can be improved and the moire of the halftone dot photo can be reduced. The image quality of both characters and photos can be improved at low cost, and the image quality can be further improved at low cost.

Thus, according to the image processing apparatus of the first aspect of the present invention, the input digital image data is irreversibly compressed by the compression means and stored in the image data storage means, and the compressed image data storage means is compressed. The image data is decompressed by the decompression means and output, and when the filter processing means performs predetermined filter processing on the digital image data, the filter processing is performed before the compression by the compression means, and the filter processing is performed. Since the post-filter processing performed after decompression by the decompression means is switched as appropriate, one filter processing means can switch between pre-filter processing and post-filter processing according to the characteristics of the image data to be processed. Therefore, it is possible to improve the image quality at low cost and to obtain an output having the characteristics expected by the user at low cost.
According to the image processing apparatus of the second aspect of the invention, if the image data information is mainly character information, the image data is mainly processed because the filter pre-processing is performed on the image data. The sharpness of the characters can be improved, and the image quality can be further improved at a low cost.
According to the image processing apparatus of the third aspect of the invention, if the information of the image data is mainly character information and photo information, post-filtering processing is performed on the image data. It can improve the sharpness of text in image data and reduce the moire of halftone photos, improve the image quality of both text and photos at low cost, and further improve the image quality at low cost. be able to.

1 is a schematic front view of a main part of an image reading apparatus to which an embodiment of an image processing apparatus of the present invention is applied. FIG. 2 is a front view of a schematic configuration of a main part during a reading operation in a book mode of the image reading apparatus of FIG. 1. FIG. 2 is a front view of a schematic configuration of a main part during a reading operation in an ADF mode of the image reading apparatus of FIG. 1. FIG. 2 is a main part circuit block configuration diagram of the image reading apparatus in FIG. 1. FIG. 5 is a detailed circuit block configuration diagram of the image processing unit in FIG. 4. FIG. 6 is a more detailed circuit block diagram of the image processing unit in FIG. 5. FIG. 2 is a functional block configuration diagram of the image reading apparatus in FIG. 1. FIG. 8 is a schematic diagram illustrating image path switching of the filter processing unit in FIG. 7. The block block diagram of the image processing apparatus of the conventional filter pre-processing type. The block block diagram of the image processing apparatus of the conventional filter post-processing type. FIG. 10 is a block diagram of a conventional filter preprocessing type image processing apparatus that performs printer γ conversion processing. The block block diagram of the image processing apparatus of the filter post-processing type which performs the conventional adaptive (gamma) conversion process. The block block diagram of the image processing apparatus provided with the two filter processing parts for the conventional pre-processing and post-processing.

DESCRIPTION OF EXEMPLARY EMBODIMENTS Hereinafter, preferred embodiments of the invention will be described in detail with reference to the accompanying drawings. The embodiments described below are preferred embodiments of the present invention, and thus various technically preferable limitations are given. However, the scope of the present invention is particularly limited in the following description. As long as there is no description which limits, it is not restricted to these aspects.
1 to 8 are diagrams showing an embodiment of an image processing apparatus of the present invention. FIG. 1 is a schematic front view of an image reading apparatus 1 to which an embodiment of the image processing apparatus of the present invention is applied. FIG.
In FIG. 1, the image reading apparatus 1 is provided with a document reading table 3 on an upper portion of a main body housing 2, and the document reading table 3 is usually provided with a contact glass. An openable / closable document pressing plate 4 is provided on the upper side of the document reading table 3, and the document pressing plate 4 is configured to bring the document G set on the document reading table 3 into close contact with the contact glass of the document reading table 3. Press down on.
An automatic paper feeder (ADF) 5 is disposed on the upper right side of the main body housing 2 in FIG. 1, and the automatic paper feeder 5 includes an ADF unit 6 and a document table 7. A stepping motor 8 is provided in the ADF unit 6, and a plurality of documents G are stacked on the document table 7. The automatic paper feeder 5 separates a plurality of documents G placed on the document table 7 one by one by the ADF unit 6 and is separated by a separation roller 17 and a transport roller 18 that are driven to rotate by a stepping motor 8. , 19 (see FIG. 3), the paper is passed through the document reading table 3 and conveyed onto a paper discharge tray (not shown).

A white reference plate 9 for shading correction is disposed at the end of the document reading table 3 on the ADF unit 6 side. The automatic paper feeder 5 has an integrated structure with the document pressing plate 4. When the document pressing plate 4 is opened, the automatic paper feeder 5 is also opened and closed together.
An exposure scanning optical system 15 including a first traveling body 10, a second traveling body 11, a lens 12, a CCD (Charge Coupled Device) 13, a stepping motor 14, and the like is disposed inside the main body housing 2. The first traveling body 10 is equipped with a light source 10a and a mirror 10b, and the second traveling body 11 is equipped with mirrors 11a and 11b.
In the exposure scanning optical system 15, the first traveling body 10 and the second traveling body are moved in the horizontal direction (sub-scanning direction) by the stepping motor 14, and a document is emitted from a light source 10 a on the first traveling body 10, for example, a fluorescent lamp. The original G placed on the reading table 3 is irradiated with light, and the reflected light of the light reflected by the original G is reflected by the mirror 10b on the first traveling body 10 toward the second traveling body 11, The light incident from the first traveling body 10 is sequentially reflected by the mirror 11 a and the mirror 11 b on the second traveling body 11 and emitted in the direction of the lens 12. The lens 12 collects and irradiates the light incident from the second traveling body 11 on the CCD 13. The CCD (line sensor) 13 has a plurality of one-dimensional CCD elements arranged as photoelectric conversion elements, photoelectrically converts incident light incident from the lens 12, and outputs analog image data (image signal). . Further, the exposure scanning optical system 15 irradiates the white reference plate 9 with light, and the reflected light from the white reference plate 9 enters the CCD 13 as described above, and outputs the white reference data from the CCD 13.
Then, as shown in FIG. 2, the image reading apparatus 1 opens a document pressing plate 4 and reads a book G image placed on the document reading table 3 as shown in FIG. As shown, a plurality of documents G placed on the document table 7 are moved one by one by rotating the plurality of rollers 17 to 19 by the stepping motor 8 of the ADF unit 6 using the automatic paper feeder 2. There is an ADF mode in which an image of the original G is read by irradiating the original G with light from the light source 10a of the first traveling body 10 which is transported to a predetermined reading position and stopped.

In the book mode, as shown in FIG. 2, the image reading apparatus 1 opens the document pressing plate 4 and sets the document G on the document reading table 3, turns on the light source 10a, and starts with the white reference. The reading of the plate 9 is performed to obtain reference data for shading correction, and then the stepping motor 14 is driven so that the first traveling body 10 and the second traveling body 11 have an optical path length from the document G to the CCD 13. The image of the original G on the original reading table 3 is read by moving in the sub-scanning direction in a constant state.
In the ADF mode, as shown in FIG. 3, when a plurality of documents G are set on the document table 7, the image reading apparatus 1 first turns on the light source 10 a to turn on the white reference plate 9. After reading, the stepping motor 8 is driven to separate the document G set on the document table 7 one by one by the separation roller 17 and conveyed by the conveyance rollers 18 and 19, and the first traveling body. Transport to 10 predetermined reading positions. At this time, the document G is conveyed at a constant speed, and the first traveling body 10 and the second traveling body 11 are stopped, and light is applied to the conveyed document G from the light source 10a on the first traveling body 10. Then, the light from the original G reflected by the original G is reflected by the mirror 10b and the mirrors 11a and 11b on the second traveling body 11, is incident on the CCD 13 through the lens 12, is photoelectrically converted by the CCD 13, and the original G image is read.

The image reading apparatus 1 has a circuit block configuration as shown in FIG. 4, and includes a central processing unit (CPU) 20, a read only memory (ROM) 21, a random access memory (RAM) 22, a light source driver 23, and a light source 10a. , A CCD drive unit 24, a CCD 13, an image processing unit 25, a scan buffer 26, a buffer controller 27, an I / F controller 28, a motor driver 29, a stepping motor 14, a motor driver 30, a stepping motor 8, and the like.
The ROM 21 stores various programs such as a basic processing program as the image reading device 1 and a filter switching processing program to be described later, and various data necessary for executing these various programs. Various data necessary for the operation of the device 1 are stored. Based on the program in the ROM 21, the CPU 20 controls each part of the image reading device 1 while using the RAM 22 as a work memory, executes a sequence as the image reading device 1, and performs a filter switching process to be described later. .
The light source 10 a is controlled to be turned on / off by the light source driver 23 under the control of the CPU 20, and the CCD 13 is driven by the CCD driving unit 24 and outputs the photoelectrically converted image data to the image processing unit 25.
The stepping motor 8 is driven by a motor driver 30, and the stepping motor 14 is driven by a motor driver 29.
A scanner buffer (image data storage unit) 26 is connected to the image processing unit 25, and the image processing unit 25 includes an analog video processing unit 41, a shading correction processing unit 42, an image data processing unit, as shown in FIG. Unit 43, timing generation unit 44, binarization processing unit 45, and the like.

The analog video processing unit 41 receives the analog image signal Sa output from the CCD 13, and the analog video processing unit 41 converts the analog image signal Sa to digital and outputs it as digital image data to the shading correction processing unit 42. To do.
The shading correction processing unit 42 stores image data when the white reference plate 9 is read as reference data in the internal RAM, performs shading correction on the image data when the original G is read based on the reference data, The image data after shading correction is output to the image data processing unit 43.
The image data processing unit 43 performs various types of image processing on the image data that has been subjected to the shading correction by the shading correction processing unit 42 based on the enable signal EN input from the timing generation unit 44, and outputs to the binarization processing unit 45. The binarization processing unit (compression unit, decompression unit) 45 outputs the processed image data to binary data or multi-value data by irreversibly compressing the image data and outputs the data to the scanner buffer 26. Also, the compressed image data in the scanner buffer 26 is decompressed. For example, the image data processing unit 43 stores image data for several lines in a line buffer, forms a matrix, and performs a spatial filter process on the image data. The timing generation unit 44 outputs stepping pulses SP to the motor driver 29 and the motor driver 30 and controls the driving timing of the stepping motor 14 and the stepping motor 8 via the motor driver 29 and the motor driver 30.

The image data Sb that has been subjected to image processing by the image processing unit 25 is accumulated in the scan buffer 26 under the control of the buffer controller 27, and other information processing apparatus (not shown) such as a personal computer via the I / F controller 28. It is output to a computer etc.
Specifically, as shown in FIG. 6, the image processing unit 25 includes a preamplifier circuit 51, a variable amplifier circuit 52, an A / D converter 53, a black arithmetic circuit 54, a shading correction arithmetic circuit 55, a line buffer 56, and the like. ing.
In the image reading apparatus 1, the reflected light irradiated on the original G on the original reading table 3 by the light source 10 a is condensed by the lens 12 through the shading adjustment plate 16 and imaged on the CCD 13. In FIG. 6, a mirror for folding the reflected light is omitted for the sake of simplicity. The shading adjustment plate 16 plays a role of adjusting the amount of light for eliminating the difference in the amount of reflected light between the central portion and the end portion of the CCD 13. That is, in the shading calculation process, if there is too much difference in the amount of reflected light between the central part and the end of the CCD 13, only a calculation result including a large amount of distortion can be obtained. After the elimination, shading calculation processing is performed.
The preamplifier circuit 51 and the variable amplifier circuit 52 constitute the analog video processing unit 41, and the A / D converter 53, the black arithmetic circuit 54, the shading correction arithmetic circuit 55, and the line buffer 56 constitute the shading correction processing unit 42. is doing.
Then, the image data processing unit 43 performs various data processing such as adaptive γ conversion processing for switching the image processing depending on whether it is edge or non-edge on the shading corrected image data input from the shading correction processing unit 42, Filter processing such as edge enhancement filter processing is performed.

The image data processing unit 43 is controlled by the CPU 20 whether or not to perform this filtering process and what filtering process to perform.
Therefore, the image reading apparatus 1 functionally includes a reading unit 61, a filter processing unit 62, a compression unit 63, a storage unit 64, an expansion unit 65, an adaptive γ conversion unit 66, and a gradation conversion process, as shown in FIG. It can be expressed by the section 67 and the output section 68.
The filter processing unit 62 compresses the image data read by the reading unit 61 using the compression unit 63 and stores it in the storage unit 64. The filter processing unit 62 stores the filter data in the storage unit 64. Filter processing is performed on the subsequent image data obtained by decompressing the image data by the decompression unit 65, then adaptive γ conversion processing is performed by the adaptive γ conversion unit 66, and gradation conversion processing is performed by the gradation conversion processing unit 67. Thus, which of the post-filter processes output from the output unit 68 is to be performed is switched under the control of the CPU 20.

  That is, as shown in FIG. 8, the filter processing unit 62 switches the flow of image data to the filter operation unit 70 that performs filter processing by switching between the register A and the register B for switching, for example, Switch between pre-filter processing and post-filter processing. For example, when the filter processing unit 62 is connected to the register B side, in the previous stage, the image data from the previous stage input does not enter the filter operation unit 70 and passes from the previous stage output to the storage unit 64 side, and from the storage unit 64 side. The image data from the subsequent stage input enters the filter calculation unit 70 via the register B, and after the filter processing is performed by the filter calculation unit 70, the image data is output from the subsequent stage output and the filter post-processing is performed. Further, the filter processing unit 62 is connected to the register A side when performing the filter preprocessing, and the image data from the previous stage input first enters the filter calculation unit 70 and the filter calculation unit 70 performs the filter processing. After that, the pre-filter processing is performed from the pre-stage output to the storage unit 64 side. Then, when the image data from the storage unit 64 is input from the subsequent stage input, if it remains on the register A side, the image data from the subsequent stage input from the storage unit 64 side is directly output from the subsequent stage output via the register A. Will come out. In addition, when the image data on which the filter preprocessing has been performed is input from the latter stage input on the storage unit 64 side, if it is switched to the register B side, the filter postprocessing is performed, and the filter preprocessing and the filter postprocessing are performed. Do both.

Next, the operation of the present embodiment will be described. The image reading apparatus 1 according to the present embodiment includes only one image data processing unit 43 as the filter processing unit 62, and appropriately determines whether to perform filter processing before compression or decompression or to perform filter processing after compression or decompression. Change over.
That is, the image reading apparatus 1 has a book mode shown in FIG. 2 and an ADF mode shown in FIG. 3 as document reading modes. In the book mode, as shown in FIG. 2, the image reading apparatus 1 opens the document pressing plate 4 and sets the document G on the document reading table 3, turns on the light source 10a, and starts with the white reference. The reading of the plate 9 is performed to obtain reference data for shading correction, and then the stepping motor 14 is driven so that the first traveling body 10 and the second traveling body 11 have an optical path length from the document G to the CCD 13. The image of the original G on the original reading table 3 is read by moving in the sub-scanning direction in a constant state. In the ADF mode, as shown in FIG. 3, when a plurality of documents G are set on the document table 7, the image reading apparatus 1 first turns on the light source 10 a to turn on the white reference plate 9. After reading, the stepping motor 8 is driven to separate the document G set on the document table 7 one by one by the separation roller 17 and conveyed by the conveyance rollers 18 and 19, and the first traveling body. Transport to 10 predetermined reading positions. At this time, the document G is conveyed at a constant speed, and the first traveling body 10 and the second traveling body 11 are stopped, and light is applied to the conveyed document G from the light source 10a on the first traveling body 10. Then, the light from the original G reflected by the original G is reflected by the mirror 10b and the mirrors 11a and 11b on the second traveling body 11, is incident on the CCD 13 through the lens 12, is photoelectrically converted by the CCD 13, and the original G image is read.

The CCD 13 outputs the image data of the original G read in this way to the image processing unit 25, and the image processing unit 25, as shown in FIG. 5, the analog video processing unit 41, the shading correction processing unit 42, the image A data processing unit 43, a timing generation unit 44, a binarization processing unit 45, and the like are provided.
The analog video processing unit 41 digitally converts the analog image signal Sa input from the CCD 13 and outputs the digital image data to the shading correction processing unit 42. The shading correction processing unit 42 reads the white reference plate 9. Is stored as reference data in the internal RAM (line buffer 56 in FIG. 6), shading correction is performed on the image data when the original G is read based on the reference data, and the shading corrected The image data is output to the image data processing unit 43.

The image data processing unit 43 performs various types of image processing, particularly filter processing, on the image data that has been subjected to the shading correction by the shading correction processing unit 42 based on the enable signal EN input from the timing generation unit 44, and performs binary processing. The binarization processing unit 45 converts the image data subjected to the image processing into binary data or multivalued data, and outputs the data to the scanner buffer 26.
Then, the image data processing unit 43 compresses and stores the compressed image data in the scanner buffer 26 and the filter preprocessing for performing the filter processing before storing the compressed image data in the scanner buffer 26 which is the storage unit 64 shown in FIG. As shown in FIG. 8, post-filtering processing for filtering after decompressing the image data is performed by switching the register A and the register B as appropriate under the control of the CPU 20.
For example, the image data processing unit 43 performs pre-filter processing if much of the information on the original G is character information, and performs post-filter processing if much of the information on the original G is text and photographs. Only one or both of the pre-filter processing and post-filter processing may be performed. Further, the pre-filtering process and the post-filtering process are determined by the user of the image reading apparatus 1 from the information on the original G to be read by the image reading apparatus 1, and an instruction operation is performed from the operation unit of the image reading apparatus 1. The CPU 20 may perform switching control between filter pre-processing and filter post-processing according to the above, or the image reading apparatus 1, for example, the image data processing unit 43 may appropriately determine from the image of the document G, and the CPU 20 may perform the filter pre-processing. Switching control of filter post-processing may be performed.

As described above, the image reading apparatus 1 according to the present embodiment irreversibly compresses input digital image data and stores it in the scanner buffer 26, and decompresses and outputs the compressed image data in the funa buffer 26. When performing predetermined filter processing on the digital image data by the image data processing unit 43 serving as filter processing means, the filter processing is performed before the compression of the image data, and the filter processing is performed after the image data is expanded. The filter post-processing to be performed is appropriately switched.
Therefore, the image data processing unit 43, which is one filter processing means, can appropriately switch between pre-filter processing and post-filter processing according to the characteristics of the image data to be processed, thereby improving image quality at low cost. Therefore, it is possible to obtain an output having characteristics expected by the user at low cost.

Further, when the image data information is mainly character information, the image reading apparatus 1 of the present embodiment performs pre-filter processing on the image data.
Therefore, it is possible to improve the sharpness of characters of image data whose main information is characters, and to further improve the image quality at low cost.
Furthermore, when the image data information is mainly text information and photographic information, the image reading apparatus 1 according to the present embodiment performs post-filtering processing on the image data.
Therefore, it is possible to improve the sharpness of characters in image data whose main information is characters and photos and reduce the moire of halftone photos, and to improve the image quality of both characters and photos at a low cost. The image quality can be further improved.
The invention made by the present inventor has been specifically described based on the preferred embodiments. However, the present invention is not limited to the above, and various modifications can be made without departing from the scope of the invention. Needless to say.

DESCRIPTION OF SYMBOLS 1 Image reading device 2, Main body case 3, Document reading stand, 4 Document pressing plate, 5 Automatic paper feeder (ADF), 6 ADF unit, 7 Document stand, 8 Stepping motor, 9 White reference plate, 10 1st driving | running | working Body, 10a light source, 10b mirror, 11 second traveling body, 11a, 11b mirror, 12 lens, 13 CCD, 14 stepping motor, 15 exposure scanning optical system, 16 original, 17 separation roller, 18, 19 transport roller, 20 CPU , 21 ROM, 22 RAM, 23 Light source driver, 24 CCD drive unit, 25 Image processing unit, 26 Scan buffer, 27 Buffer controller, 28 I / F controller, 29 Motor driver, 30 Motor driver, 41 Analog video processing unit, 42 Shading correction processing unit, 43 image data processing unit, 44 timing generation unit, 45 binarization processing unit, 51 preamplifier circuit, 52 variable amplification circuit, 53 A / D converter, 54 black arithmetic circuit, 55 shading correction arithmetic circuit, 56 line buffer, 61 reading unit, 62 filter processing unit , 63 compression unit, 64 storage unit, 65 decompression unit, 66 adaptive γ conversion unit, 67 gradation conversion processing unit, 68 output unit, 70 filter operation unit, A, B register

Claims (3)

  The input digital image data is irreversibly compressed by the compression means and stored in the image data storage means. The compressed image data of the image data storage means is decompressed by the decompression means and output, and the digital image data is predetermined as digital image data. An image processing apparatus comprising filter processing means for performing the filter processing of the filter, wherein the filter processing by the filter processing means is performed before compression by the compression means, and the filter processing is decompressed by the decompression means. An image processing apparatus that performs switching to post-filtering processing to be performed later.   The image processing apparatus according to claim 1, wherein when the information of the image data is mainly character information, the image processing apparatus performs the pre-filtering process on the image data.   2. The image processing apparatus according to claim 1, wherein the image processing apparatus performs the post-filtering process on the image data when the information of the image data is mainly character information and photographic information. .

Images